Echo cancellation and echo suppression are methods of reducing echo in communication systems, such as telephony systems. They aim to improve signal quality by preventing echo creation or removing/reducing it after it has become present. The methods may also be referred to as acoustic echo cancellation (AEC) and acoustic echo suppression (AES). Acoustic echo may be generated due to sounds from a speaker being reflected and recorded by a microphone, while line echo, which may also be present, is based on reflections occurring in the communication system itself. In general, the goal of AEC and AES is to prevent a speaking individual from hearing an echo of their own speech.
AEC may operate by subtracting the echo from a signal that may be received by the speaker. AES, on the other hand, may detect a signal going in one direction and then insert an amount of loss into a line of the other direction. For example, an echo suppressor at a far-end of a communication system adds the loss when it detects a signal coming from a near-end of the communication system. The injected loss may prevent the speaker at the far-end from hearing their own voice by reducing the echo to imperceptible levels.
While AEC and AES may work as desired when two parties speak separately, periods of time when both parties speak concurrently may be a problem, however. Both parties speaking concurrently may be referred to as double talk. If AEC and/or AES is performed during periods of double talk, there is a chance that all speech is either eliminated or suppressed so that neither party is heard. Many techniques have been employed to implement AEC and/or AES during periods of double talk. However, some of these methods may not entirely cancel or suppress echo during double talk, or even appropriately detect double talk. As such, robust double talk detection may be desired when implementing AES.
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